1. Field of the Invention
The present invention relates to machinery for the handling of very large thin sheets, and, more particularly, to a device for assembling a number of different panel layers, including carrier panels and outer layers, into a press pack, for the production of layered pressed panels and decorative panels, or for the application of coated paper sheets, liners, veneer sheets, plastic films, etc., to panels of chipboard, fiber, metal, plastic, or plywood, the various panel layers being mechanically singulated off corresponding layer stacks and transferred to a collecting station for assembly into a press pack, which is then fed to a panel press for curing under pressure.
2. Description of the Prior Art
In recent years, both the variety of pressed panels, in terms of their composition, and the application possibilities for such pressed panels have undergone rapid expansion and growth. Manufacturers of such panels, being under competitive pressure to look for ever greater production economies through mechanization, are increasingly using modern, highly efficient panel presses, so that it becomes necessary to also use more sophisticated panel layer assembly units and press pack feeding units, in order to fully utilize the capacity of a modern panel press of single-level or multi-level construction. At the same time, such an installation must be quickly adaptable to the production of a variety of layered pressed panels, including the application of outer layers of wood veneer, paper, and plastic to carrier panels, and the assembly of pressboard panels, sound-proofing panels, plywood panels, and furniture panels, for example. The panel layer assembly device must be capable of collecting and assembling the individual layers into a press pack, and to feed a succession of accurately assembled press packs to the panel press.
Known devices for assembling large panel layers into press packs operate either semi-automatically or fully automatically, using a vertically movable suction bank, supported on a carriage, which is suspended from overhead rails. After the carriage is moved over a large stack, its suction bank picks up a panel layer and carries it to an assembly table, where it is deposited on top of other, previously collected panel layers. The assembled press pack is then transferred from the assembly table to a press pack feeding station where it is inserted into the panel press by means of a roller conveyor, or a belt conveyor, or with the aid of transfer panels of sheet metal.
A more advanced layer assembly device is suggested in U.S. Pat. No. 3,914,154. This patent discloses a collecting carriage which is suspended on overhead rails and which moves from layer stack to layer stack, along a row of stack tables. At the near edge of each stack table is arranged a stationary edge lifting device with a vertically movable suction bank, capable of raising the edge of the uppermost panel layer, while the collecting carriage advances over the layer stack, thereby sliding a collecting palette, which carries on it a partially assembled press pack, under the partially raised layer.
Great care must be taken to avoid damage to the thin panel layers during collection, the risk of damage being particularly high in connection with thin and very large panel layers. It has therefore become necessary to completely mechanize the layer collecting procedure. Nevertheless, the time required for assembling a complete press pack from a large number of layer stacks, and for transferring it to the panel press is oftentimes too long, in comparison to the duration of the pressing cycle of a modern panel press. The situation becomes quite unbalanced in the case of certain layered pressed panels which require panel packs composed of up to eight different panel layers, in order to obtain the desired surface pattern, coloring, and/or mechanical characteristics, or in the case of chipboard panels which have to be covered with up to three outer layers on each side. The discrepancy of output performance is particularly severe in the case of panel presses which are of the multi-level type, or in the case of so-called rapid cycling panel presses which are capable of pressing several successive press packs simultaneously.
A partial reason for the relative inefficiency of the known panel layer assembly devices lies in their inadequate acceleration characteristics, as well as in their inability of repeatedly stopping with great accuracy, for a precise positioning of the panel layers in the panel layer collecting station.